Method for coloring an optical element in a non-uniform linear pattern

ABSTRACT

A method for coloring an optical element in a non-uniform linear pattern is provided. The method includes (a) preparing at least one colorant composition containing at least one photochromic material; (b) depositing the colorant composition on at least one surface of the optical element in a controlled, predetermined pattern using an inkjet printing apparatus to provide a linearly gradient color pattern on the optical element when the optical element is exposed to actinic radiation; and (c) drying the colorant composition on the surface of the optical element. An optical element prepared by the method also is provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is the United States national phase of InternationalApplication No. PCT/US2015/019690 filed Mar. 10, 2015, which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention is directed to a method for preparing a coloredoptical element in a non-uniform linear pattern, such as a linearlygradient color pattern, using an inkjet printing apparatus.

BACKGROUND OF THE INVENTION

Gradient tinting methods are known for use in coloring optical elements,such as lenses. The gradient tinting effect provides a functionaladvantage in that the lens generally has a higher color density at thetop of the lens for improved distance viewing with less color density atthe bottom of the lens, and an aesthetic effect for fashion and style.

Further, there are well known methods for applying a photochromiccomposition to optical elements. For example, photochromic materials maybe incorporated into the substrate components used to form the opticalelement. Alternatively, the photochromic materials may be applied to thesurface of the optical element and permitted to penetrate into thesurface region (known as imbibition). Additionally, the photochromicmaterial can be applied to the optical element as a coating by knownmethods, such as spin coating, dip coating, spray coating, and the like.

Methods have been disclosed to achieve a gradient photochromic opticalelement. Generally, gradient tinting of eyewear lenses is accomplishedby dipping or submerging the lens into a dye bath. This process requiresmore precise and reproducible processing than is required for solidtinting or coloring. Moreover, some optical substrates, such aspolycarbonate lens material, absorb dyes very poorly. While methods havebeen developed to overcome these processing difficulties, such methodsoften require additional manufacturing steps, thus adding additionalmanufacturing costs.

Accordingly, it would be desirable to provide a cost-effective method ofpreparing a gradient photochromic optical element where a photochromiccomposition can be applied in a controlled and predetermined gradientcolor pattern (upon exposure to actinic radiation) to the surface of theoptical element.

SUMMARY OF THE INVENTION

The present invention provides a method for coloring an optical elementin a non-uniform linear pattern. The method comprises (a) preparing atleast one colorant composition comprising at least one photochromicmaterial; (b) depositing the colorant composition on at least onesurface of the optical element in a controlled, predetermined patternusing an inkjet printing apparatus to provide a linearly gradient colorpattern on the optical element when the optical element is exposed toactinic radiation; and (c) drying the colorant composition on thesurface of the optical element. An optical element prepared by themethod of the present invention also is provided.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise indicated, all ranges or ratios disclosed herein are tobe understood to encompass any and all sub-ranges or sub-ratios subsumedtherein. For example, a stated range or ratio of “1 to 10” should beconsidered to include any and all sub-ranges between (and inclusive of)the minimum value of 1 and the maximum value of 10. That is, allsub-ranges or sub-ratios beginning with a minimum value of 1 or more andending with a maximum value of 10 or less, such as, but not limited to,1 to 6.1; 3.5 to 7.8; and 5.5 to 10.

As used herein and in the claims, the term “polymer” and like terms,such as “polymeric”, means homopolymers (prepared from a singlemonomer), copolymers (prepared from two or more different monomers), andgraft polymers, including but not limited to comb graft polymers, stargraft polymers, and dendritic graft polymers.

As used in this specification and the appended claims, the articles “a”,“an”, and “the” include plural referents unless expressly andunequivocally limited to one referent.

Additionally, for the purposes of this specification, unless otherwiseindicated, all numbers expressing quantities of ingredients, reactionconditions, and other properties or parameters used in the specificationare to be understood as being modified in all instances by the term“about”. Accordingly, unless otherwise indicated, it should beunderstood that the numerical parameters set forth in the followingspecification and attached claims are approximations. At the very least,and not as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, numerical parameters should beread in light of the number of reported significant digits and theapplication of ordinary rounding techniques.

As previously mentioned, the present invention is directed to a methodfor coloring an optical element in a non-uniform linear pattern, such asa linearly gradient color pattern. For purposes of the presentinvention, a “linearly gradient color pattern” is achieved through thedeposition via inkjet printing techniques, of a photochromic compositioncomprising photochromic dyes (which are described in further detailherein below) to create a gradual, visually discernible variation in hueand/or color density over an area of the optical element when theoptical element is exposed to actinic radiation. The gradual variationin hue and/or color density occurs across the surface of the opticalelement in one direction. For example, when the optical element is alens, the variation in hue and/or color density can occur from thebottom of the lens to top of the lens. That is, the deposition of aparticular composition occurs across the lens from one side to the othersuch that the variation in hue and/or color density occurs from thebottom to the top or vice versa. The term “hue” as used herein meanspure color expressed in terms such as “green”, “red” or “magenta”; andincludes mixtures of two pure colors like “red-yellow” (i.e., “orange”)or “yellow-green”. The term “color density” as used herein means, uponexposure to actinic radiation, optical density of an area of the opticalelement surface printed with the colorant composition. A higher colordensity results in a lower percent light transmittance. For purposes ofthis invention, the bottom of the lens is closest to the lens wearer'scheekbone, and the top of the lens is closest to the lens wearer'sforehead. This linearly gradient color pattern should be differentiatedfrom radially gradient color patterns known in the art, e.g., those usedin connection with lenses, wherein color density varies radially outwardfrom a center point to the outer perimeter of the lens.

The optical element can be any of those known in the art. Generally, theoptical element is selected from the group consisting of lenses,windows, display elements, goggles, visors, face shields, automotivetransparencies, e.g., sunroofs and light covers, aerospacetransparencies, and wearable transparencies. Further, the opticalelement used in the method of the present invention can be substantiallytransparent, or it may possess a uniform color (e.g., the opticalelement may be tinted), prior to deposition of the aforementionedcolorant composition.

In a particular embodiment, the optical element is a lens. The lens canbe an ophthalmic lens. As used herein, the term “optical” meanspertaining to or associated with light and/or vision. As used herein,the term “ophthalmic” means pertaining to or associated with the eye andvision. Non-limiting examples of ophthalmic elements include correctiveand non-corrective (piano) lenses, including single vision ormulti-vision lenses, which may be either segmented or non-segmentedmulti-vision lenses (such as, but not limited to, bifocal lenses,trifocal lenses, and progressive lenses), as well as other elements usedto correct, protect, or enhance (cosmetically or otherwise) vision,including without limitation, contact lenses, intra-ocular lenses,magnifying lenses, and protective lenses or visors. As used herein, theterm “display” means the visible or machine-readable representation ofinformation in words, numbers, symbols, designs, or drawings.Non-limiting examples of display elements and devices include screensand monitors. As used herein, the term “window” means an apertureadapted to permit the transmission of radiation therethrough.

The optical element can comprise any of the optical substrates wellknown in the art. The substrate may comprise a polymeric organicmaterial chosen from thermosetting polymeric organic materials,thermoplastic polymeric organic materials, or a mixture of suchpolymeric organic materials. The polymeric organic material can bechosen from poly(C₁-C₁₂ alkyl methacrylates), poly(oxyalkylenedimethacrylates), poly(alkoxylated phenol methacrylates), celluloseacetate, cellulose triacetate, cellulose acetate propionate, celluloseacetate butyrate, poly(vinyl acetate), poly(vinyl alcohol), poly(vinylchloride), poly(vinylidene chloride), thermoplastic polycarbonates,polyesters, polyurethanes, polythiourethanes, polysulfithiourethanes,poly(urea-urethane), poly(ethylene terephthalate), polystyrene,poly(alpha methylstyrene), copoly(styrene-methylmethacrylate),copoly(styrene-acrylonitrile), polyvinyl butyral or polymers preparedfrom bis(allyl carbonate) monomers, polyfunctional acrylate monomers,polyfunctional methacrylate monomers, diethylene glycol dimethacrylatemonomers, diisopropenyl benzene monomers, ethoxylated bisphenol Adimethacrylate monomers, ethylene glycol bismethacrylate monomers,poly(ethylene glycol) bismethacrylate monomers, ethoxylated phenolbismethacrylate monomers, alkoxylated polyhydric alcohol polyacrylatemonomers, styrene monomers, urethane acrylate monomers, glycidylacrylate monomers, glycidyl methacrylate monomers, diallylidenepentaerythritol monomers, or mixtures of such monomers.

Substrates suitable for use in the preparation of optical elements ofthe present invention typically demonstrate a refractive index of atleast 1.55 and can include non-plastic substrates, such as glass. Moreoften, substrates commonly used in optical applications are used,including polyol(allyl carbonate) monomers, e.g., allyl diglycolcarbonates such as diethylene glycol bis(allyl carbonate), which monomeris sold under the registered trademark CR-39 by PPG Industries, Inc.;poly(urea)urethane polymers, which are prepared, for example, by thereaction of a polyurethane prepolymer and a diamine curing agent, acomposition for one such polymer being sold under the registeredtrademark TRIVEX by PPG Industries, Inc.; polyol(meth)acryloylterminated carbonate monomer; diethylene glycol dimethacrylate monomers;ethoxylated phenol methacrylate monomers; diisopropenyl benzenemonomers; ethoxylated trimethylol propane triacrylate monomers; ethyleneglycol bismethacrylate monomers; poly(ethylene glycol) bismethacrylatemonomers; urethane acrylate monomers; poly(ethoxylated bisphenol Adimethacrylate); poly(vinyl acetate); poly(vinyl alcohol); poly(vinylchloride); poly(vinylidene chloride); polyethylene; polypropylene;polyurethanes; polythiourethanes; thermoplastic polycarbonates, such asthe carbonate-linked resin derived from bisphenol A and phosgene, onesuch material being sold under the registered trademark LEXAN by SabicGlobal Technologies; polyesters, such as the material sold under theregistered trademark MYLAR by Dupont Teijin Films; poly(ethyleneterephthalate); polyvinyl butyral; poly(methyl methacrylate), such asthe material sold under the registered trademark PLEXIGLAS by ArkemaFrance Corporation, and polymers prepared by reacting polyfunctionalisocyanates with polythiols or polyepisulfide monomers, eitherhomopolymerized or co- and/or terpolymerized with polythiols,polyisocyanates, polyisothiocyanates, and, optionally, ethylenicallyunsaturated monomers or halogenated aromatic-containing vinyl monomers.Also contemplated are copolymers of such monomers and blends of thedescribed polymers and copolymers with other polymers, e.g., to forminterpenetrating network products.

As mentioned above, in the method of the present invention, a colorantcomposition is prepared and deposited on at least one surface of theoptical element, such as any of those previously described. The colorantcomposition comprises a photochromic material. Photochromic materialsuseful in the method of the present invention comprise at least onephotochromic compound selected from the group consisting of pyrans,spiropyrans, oxazines, spiroxazines, fulgides, fulgimides, metallicdithizonates, diarylethenes, and mixtures thereof. Specific butnon-limiting examples of suitable photochromic materials can includeindeno-fused naphthopyrans, naphtho[1,2-b]pyrans, naphtho[2,1-b]pyrans,spirofluoroeno[1,2-b]pyrans, phenanthropyrans, quinolinopyrans,fluoroanthenopyrans, spiropyrans, benzoxazines, naphthoxazines,spiro(indoline)naphthoxazines, spiro(indoline)pyridobenzoxazines,spiro(indoline)fluoroanthenoxazines, spiro(indoline)quinoxazines,fulgides, fulgimides, diarylethenes, diarylalkylethenes, anddiarylalkenylethenes.

As used herein, the term “photochromic” and similar terms, such as“photochromic compound”, includes thermally reversible photochromiccompounds, and non-thermally reversible photochromic compounds, andmixtures thereof. The term “thermally reversible photochromiccompounds/materials” as used herein means compounds/materials capable ofconverting from a first state (i.e., unactivated or clear state) to asecond state (i.e., activated or colored state) in response to actinicradiation, and reverting back to the first state in response to thermalenergy. The term “non-thermally reversible photochromiccompounds/materials” as used herein means compounds/materials capable ofconverting from a first state (i.e., clear or unactivated state) to asecond state (i.e., activated or colored state) in response to actinicradiation; and reverting back to the first state in response to actinicradiation of substantially the same wavelength(s) as the absorption(s)of the colored state.

In addition to the photochromic material, the colorant composition cancomprise one or more polymeric components. Examples of suitablepolymeric components can include, but are not limited to, the followingpolymers or precursors thereof: polyvinyl alcohol, polyvinyl chloride,polyurethane, polyacrylate, and polycaprolactam. The colorantcomposition can be a thermoplastic composition or a thermosettingcomposition. In a particular embodiment of the present invention, thecolorant composition can be a curable composition comprising aphotochromic material, a curable resin composition, and, optionally, asolvent.

The curable resin composition typically includes a first reactant (orcomponent) having functional groups, e.g., hydroxyl functional polymerreactant; and a second reactant (or component) that is a crosslinkingagent having functional groups that are reactive towards and that canform covalent bonds with the functional groups of the first reactant.The first and second reactants of the curable resin composition can eachindependently include one or more functional species, and are eachpresent in amounts sufficient to provide cured coatings having adesirable combination of physical properties, e.g., smoothness, solventresistance, and hardness.

Examples of curable resin compositions that can be used with the curableresin compositions include, but are not limited to, curable resincompositions that include an epoxide functional polymer, such as(meth)acrylic polymers containing residues of glycidyl(meth)acrylate,and an epoxide reactive crosslinking agent (e.g., containing activehydrogens, such as hydroxyls, thiols, and amines); curable resincompositions that include active hydrogen functional polymer, such ashydroxy functional polymer and capped (or blocked) isocyanate functionalcrosslinking agent; and curable resin compositions that include activehydrogen functional polymer, such as hydroxy functional polymer, andaminoplast crosslinking agent.

With some aspects of the present invention, the colorant compositioncomprises a photochromic material and a curable resin composition whichis a curable urethane (or polyurethane) resin composition. In additionto the photochromic material, such a curable urethane compositiontypically contains an active hydrogen functional polymer, such as anamino functional polymer or a hydroxy functional polymer; and a capped(or blocked) isocyanate functional crosslinking agent. Active hydrogenfunctional polymers are well known in the art. Hydroxy functionalpolymers that can be used in such compositions include, but are notlimited to, art-recognized hydroxy functional vinyl polymers, hydroxyfunctional polyesters, hydroxy functional polyurethanes, and mixturesthereof.

Vinyl polymers having active hydrogen groups, such as hydroxy functionalgroups, can be prepared by free radical polymerization methods that areknown to those of ordinary skill in the art. With some aspects of thepresent invention, a hydroxy functional vinyl polymer is prepared from amajority of (meth)acrylate monomers and is referred to herein as a“hydroxy functional (meth)acrylic polymer”.

Hydroxy functional polyesters useful in curable coating compositionsthat include capped isocyanate functional crosslinking agents can beprepared by art-recognized methods. Typically, diols and dicarboxylicacids or diesters of dicarboxylic acids are reacted in a proportion suchthat the molar equivalents of hydroxy groups is greater than that ofcarboxylic acid groups (or esters of carboxylic acid groups) with theconcurrent removal of water or alcohols from the reaction medium.

Hydroxy functional urethanes can be prepared by art-recognized methods.Typically, one or more difunctional isocyanates are reacted with one ormore materials having two active hydrogen groups (e.g., diols ordithiols), such that the ratio of active hydrogen groups to isocyanategroups is greater than 1, as is known to the skilled artisan.

By “capped (or blocked) isocyanate crosslinking agent” is meant acrosslinking agent having two or more capped isocyanate groups that candecap (or deblock) under cure conditions, e.g., at elevated temperature,to form free isocyanate groups and free capping groups. The freeisocyanate groups formed by decapping of the crosslinking agent aretypically capable of reacting and forming substantially permanentcovalent bonds with the active hydrogen groups of the active hydrogenfunctional polymer (e.g., with the hydroxy groups of a hydroxyfunctional polymer).

It is desirable that the capping group of the capped isocyanatecrosslinking agent not adversely affect the curable coating compositionupon decapping from the isocyanate (i.e., when it becomes a free cappinggroup). For example, it is desirable that the free capping group neitherbecome trapped in the cured film as gas bubbles nor excessivelyplasticize the cured film. Capping groups useful in the presentinvention typically have the characteristics of being non-fugitive orcapable of escaping substantially from the forming coating prior to itsvitrification.

Classes of capping groups of the capped isocyanate crosslinking agentcan be selected from, include, but are not limited to hydroxy functionalcompounds, e.g., linear or branched C₂-C₈ alcohols, ethylene glycolbutyl ether, phenol and p-hydroxy methylbenzoate; 1H-azoles, e.g.,1H-1,2,4-triazole and 1H-2,5-dimethyl pyrazole; lactams, e.g.,ε-caprolactam and 2-pyrolidinone; ketoximes, e.g., 2-propanone oxime and2-butanone oxime. Other suitable capping groups include, but are notlimited to, 3,5-dimethyl pyrazole, morpholine, 3-aminopropyl morpholine,and N-hydroxy phthalimide.

The isocyanate or mixture of isocyanates of the capped isocyanatecrosslinking agent typically has two or more isocyanate groups (e.g., 3or 4 isocyanate groups). Examples of suitable isocyanates that can beused to prepare the capped isocyanate crosslinking agent include, butare not limited to, monomeric diisocyanates, e.g., α,α′-xylylenediisocyanate, α,α,α′,α′-tetramethylxylylene diisocyanate, and1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane (isophoronediisocyanate or IPDI), and dimers and trimers of monomeric diisocyanatescontaining isocyanurate, uretidino, biruet, or allophanate linkages,e.g., the trimer of IPDI.

The capped isocyanate crosslinking agent can also be selected fromoligomeric capped isocyanate functional adducts. As used herein, by“oligomeric capped polyisocyanate functional adduct” is meant a materialthat is substantially free of polymeric chain extension. Oligomericcapped polyisocyanate functional adducts can be prepared byart-recognized methods from, for example, a compound containing three ormore active hydrogen groups, e.g., trimethylolpropane (TMP), and anisocyanate monomer, e.g.,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), in amolar ratio of 1:3, respectively. In the case of TMP and IPDI, byemploying art-recognized starved feed and/or dilute solution synthesistechniques, an oligomeric adduct having an average isocyanatefunctionality of 3 can be prepared (e.g., “TMP-3IPDI”). The three freeisocyanate groups per TMP-3IPDI adduct are then capped with a cappinggroup, e.g., a linear or branched C₂-C₈ alcohol.

To catalyze the reaction between the isocyanate groups of the cappedpolyisocyanate crosslinking agent and the active hydrogen groups of theactive hydrogen functional polymer, one or more catalysts are typicallypresent in the curable photochromic coating composition in amounts offrom, for example, 0.1 to 5 percent by weight, based on total resinsolids of the composition. Classes of useful catalysts include, but arenot limited to, urethanization catalysts such as organic tin compounds,e.g., tin(II) octanoate and dibutyltin(IV) dilaurate, as well as bismuthcompounds, zinc compounds and salts thereof, zirconium compounds andsalts thereof, carboxylates, and tertiary amines, e.g.,diazabicyclo[2.2.2]octane. Mixtures of catalysts can be used.

It should be understood that any of the photochromic coatings known inthe art can be used as the colorant composition in the method of thepresent invention. For example, suitable photochromic coatings caninclude those described in U.S. Pat. No. 7,189,456 at column 20 line 49to column 24 line 6, the recited portions of which are incorporated byreference herein.

The colorant compositions useful in the method of the present inventionoptionally further include a solvent. Examples of suitable solvents caninclude, but are not limited to, acetates, alcohols, ketones, glycols,ethers, aliphatics, cycloaliphatic, and aromatics. Examples of suitableacetates include, but are not limited to, ethyl acetate, butyl acetate,and glycol acetate. Examples of suitable ketones include, but are notlimited to, methyl ethyl ketone and methyl-N-amyl ketone. Examples ofsuitable aromatics include, but are not limited to, toluene,naphthalene, and xylene. In one aspect of the present invention, one ormore solvents can be added to each of the first reactant and the secondreactant. Suitable solvent blends can include, for example, one or moreacetates, propanol and its derivatives, one or more ketones, one or morealcohols, and/or one or more aromatics.

The colorant compositions useful in the method of the present inventionoptionally contain additives, such as rheology additives for flow andwetting, e.g., poly(2-ethylhexyl)acrylate, adjuvant resin to modify andoptimize coating properties, antioxidants hindered amine lightstabilizers (HALS) and ultraviolet light absorbers (UVA), e.g.,hydroxyphenylbenzotriazole, hydroxybenzophenones,hydroxyphenyl-s-triazines, oxanalides. Examples of useful antioxidants,HALS, and UVAs include those available commercially from BASF under thetrademarks IRGANOX and TINUVIN.

As previously mentioned, in the method of the present invention thecolorant composition is deposited on at least one surface of the opticalelement in a controlled predetermined pattern using an inkjet printingapparatus so as to provide a linearly gradient color pattern on theoptical element upon exposure of the optical element to actinicradiation. The inkjet printing apparatus applies a colorant compositionin the form of extremely fine droplets on the surface of the opticalelement. A discharge apparatus associated with the printing apparatus,such as one or more print heads, has one or more nozzles associatedtherewith. Each of the nozzles is configured to controllably discharge asingle droplet of the composition, either continuously or on-demand. Inthe on-demand system, the discharge of droplets is controlled by acontroller having pre-determined droplet discharge profile. For example,the controller may control the size of the drop (volume of colorantcomposition) and the speed at which the drop is formed and delivered. Insome aspects of the present invention, the one or more print heads maybe provided with one or more piezoelectric elements that provide amechanism for forming and discharging the droplets from the one or moreprint heads. A voltage applied to the one or more piezoelectricelements, such as a control voltage determined by the controller,changes the shape of the one or more piezoelectric elements, therebygenerating a pressure pulse in the colorant composition, which forces adroplet of the composition from the nozzle. The controller directs oneor more print heads to generate droplets on demand. In this manner, thetiming, position, and volume of colorant composition delivered per unitof area of the printing surface can be controlled.

In other aspects of the present invention, a thermal ink jet apparatuscan be employed. That is, the one or more print heads may have at leastone chamber including a heater. A droplet is ejected from the chamberwhen a pulse of voltage is passed across the heater, such as a controlvoltage determined by the controller. Such a voltage differential causesa rapid vaporization of the colorant composition in the chamber andforms a bubble. Formation of the bubble causes a pressure differentialwithin the chamber, thereby propelling a droplet of the composition ontothe coating surface. The controller directs one or more print heads togenerate droplets on demand. In this manner, the timing, position, andvolume of coating material delivered per unit of area of the printingsurface can be controlled.

Each droplet discharged from the nozzle of the print head is depositedon the surface of the optical element in the form of a single dot. Thus,assembly of deposited droplets creates an array that enables a patternto be formed. In this manner, all or portions of the printing surfacemay be coated. In accordance with the present invention, when one ormore portions of the optical element surface are printed, a controlled,predetermined pattern may be formed on the surface, such that, uponexposure to actinic radiation, a linearly gradient color pattern isobserved.

Each print head is in fluid communication with a storage reservoir. Whenthe printing apparatus has more than one print head, individual storagereservoirs may be provided for each print head. Each storage reservoiris configured to store a colorant composition (or composition free ofphotochromic material) to be delivered to the one or more print heads.In this manner, it is possible to print a plurality of differentcompositions at the same time by using a plurality of print heads togenerate various gradient color patterns upon exposure of the opticalelement to actinic radiation. Thus, the gradient pattern may be formedon the surface of the optical element from the deposition of two or morecolorant compositions, or the gradient pattern may be formed from asingle colorant composition applied in one or more successive layers.Various additional devices, such as heaters, mixers, or the like, may beassociated with each storage reservoir for preparing the colorantcomposition prior to delivery to the one or more print heads. In someaspects of the invention, viscosity of the colorant composition may becontrolled, such as by increasing or reducing the viscosity of thecomposition, prior to loading the composition into the storage reservoiror prior to delivering the composition to the one or more print heads.

In another aspect, heating of the coating material within the print headmanifold or reservoir also may be used to control coating viscosityprior to delivering the coating material to the substrate.

The inkjet apparatus can be comprised of multiple print where each printhead is provided with (i) a different colorant composition, and (ii)optionally, at least one print head is provided with a composition freeof photochromic material. Each such composition is deposited on thesurface of the optical element in a predetermined pattern so as toprovide a linearly gradient color pattern which varies in hue and/orcolor density from one area of the optical element to another area ofthe optical element upon exposure of the optical element to actinicradiation. The composition free of photochromic material can compriseany of the aforementioned polymeric compositions used in conjunctionwith the colorant composition provided, however, that no photochromicmaterial is present. With this embodiment, the area of the opticalelement provided with the photochromic-free composition will exhibit nochange in hue and/or color density upon exposure to actinic radiation.

In another aspect of the invention, the inkjet apparatus is comprised ofmultiple print heads where each print head is provided with a differentcolorant composition. Each colorant composition is deposited on thesurface of the optical element in a predetermined pattern so as toprovide a linearly gradient color pattern which varies in hue and/orcolor density from one area of the optical element to another area ofthe optical element upon exposure of the optical element to actinicradiation.

A plurality of print heads may be arranged in an array. The plurality ofprint heads may be arranged parallel to one another in a direction thatis angled relative to a direction in which the optical element is movedrelative to the print heads. Offsetting the print heads at an anglerelative to the direction in which the optical element is moved relativeto the print heads allows a complete coverage of optical elements ofvarious shapes and sizes, for example, lenses having a convex, concaveor segmented surface. In other aspects, the print heads may be arrangedlinearly next to one other in a direction substantially parallel orperpendicular to the direction in which the optical element is movedrelative to the print heads.

During the printing process, the colorant composition (or a compositionfree of photochromic material) may be applied on the surface of theoptical element in a single pass in which the optical element is heldstationary and the one or more print heads are moved, or in which theoptical element is moved and the one or more print heads are heldstationary, or in which both the optical element and the one or moreprint heads are moved. The single pass may be performed using a singleprint head or multiple print heads. In some aspects of the presentinvention, the composition may be applied on the optical element in twoor more passes in which the optical element is held stationary and theone or more print heads are moved, or in which the optical element ismoved and the one or more print heads are held stationary, or in whichboth the optical element and the one or more print heads are moved. Twoor more passes may be performed using a single print head or multipleprint heads.

The printing apparatus may have a controller for controlling theoperation of the printing apparatus. The controller may be configuredfor controlling the printing operations of the one or more print headsand/or movement operations of the optical element and/or the one or moreprint heads. In addition, the controller may be configured to controlthe filling and delivery operations of the colorant composition in theone or more storage reservoirs. For example, the controller may includea variety of discrete computer-readable media components for controllingthe printing and/or movement operations. For example, thiscomputer-readable media may include any media that can be accessed bythe controller, such as volatile media, non-volatile media, removablemedia, non-removable media, transitory media, non-transitory media, etc.As a further example, this computer-readable media may include computerstorage media, such as media implemented in any method or technology forstorage of information, such as computer-readable instructions, datastructures, program modules, or other data; random access memory (RAM),read-only memory (ROM), electrically erasable programmable read-onlymemory (EEPROM), flash memory, or other memory technology; CD-ROM,digital versatile disks (DVDs), or other optical disk storage; magneticcassettes, magnetic tape, magnetic disk storage, or other magneticstorage devices; or any other medium which can be used to store thedesired information and which can be accessed by the controller.Further, this computer-readable media may include communications media,such as computer-readable instructions, data structures, programmodules, or other data in a modulated data signal, such as a carrierwave or other transport mechanism and include any information deliverymedia, wired media (such as a wired network and a direct-wiredconnection), and wireless media (such as acoustic signals, radiofrequency signals, optical signals, infrared signals, biometric signals,bar code signals, etc.). Of course, combinations of any of the aboveshould also be included within the scope of computer-readable media.

A user may enter commands, information, and data, such as informationrelating to an art form file of a desired printed layer, into thecontroller through certain attachable or operable input devices via auser input interface. Of course, a variety of such input devices may beutilized, e.g., a microphone, a trackball, a joystick, a touchpad, atouch-screen, a scanner, etc., including any arrangement thatfacilitates the input of data, and information to the controller from anoutside source. Still further, data and information can be presented orprovided to a user in an intelligible form or format through certainoutput devices, such as a monitor (to visually display this informationand data in electronic form), a printer (to physically display thisinformation and data in print form), a speaker (to audibly present thisinformation and data in audible form), etc. All of these devices are incommunication with the controller, e.g., through an output interface. Itis envisioned that any such peripheral output devices be used to provideinformation and data to the user.

In the method for producing the optical element in accordance with thepresent invention, the colorant composition (or composition free ofphotochromic material) may be leveled to assure a uniform thickness ofthe composition which will be or has been deposited on the surface ofthe optical element. Leveling may be performed concomitant with thedepositing step, or after the depositing step is completed. A levelingdevice may be used to accomplish this. Furthermore, leveling may beprior, concomitant, or after any additional post-processing steps afterthe depositing step but before the drying step. In some aspects, theleveling step may include vibrating the optical element. Vibration ofthe optical element may be performed linearly, for example in the formof reciprocal movement along one axis. In other aspects, vibration ofthe optical element may be performed linearly along two axes, such asvibrating the optical element linearly in one plane. In some aspects,the leveling step may include vibrating the optical element at afrequency of 10 Hz to 110 Hz. Further, the leveling step may includevibrating the optical element for 3 seconds to 30 seconds.

Once deposited in a controlled, predetermined pattern so as to form alinearly gradient color pattern on the optical element upon exposure toactinic radiation, the colorant composition (or the composition free ofphotochromic material) is dried. As used herein, the terms “dried” or“drying” means that the composition is exposed to ambient conditions orelevated temperatures in order to evaporate any solvents present; and/orthat the colorant composition is at least partially cured to promote atleast partial reaction of any reactive components present in thecolorant composition (e.g., in the case of a curable colorantcomposition). Both radiation curing and thermal curing are contemplated.

In a particular embodiment of the present invention, the optical elementis a lens, such as an ophthalmic lens, and the linearly gradient colorpattern varies in hue and/or color density from the bottom of the lensto the top of the lens upon exposure of the lens to actinic radiation.Further, upon exposure of the lens to actinic radiation, the gradientcolor pattern generally has a higher percent light transmittance at thebottom of the lens than at the top of the lens.

The optical elements prepared by the method of the present inventionoptionally can include one or more layers in addition to thephotochromic composition layer(s). Examples of such additional layersinclude, but are not limited to, primer coatings and films (typicallyapplied to the optical element surface(s) prior to deposition of thephotochromic composition); protective coatings and films (applied beforeor after deposition of the photochromic composition to the opticalelement surface, including transitional coatings and films and abrasionresistant coatings and films; anti-reflective coatings and films;polarizing coatings and films; and combinations thereof. As used herein,the term “protective coating or film” refers to coatings or films thatcan prevent wear or abrasion, provide a transition in properties fromone coating or film to another, protect against the effects ofpolymerization reaction chemicals and/or protect against deteriorationdue to environmental conditions, such as moisture, heat, ultravioletlight, oxygen, etc.

As used herein, the term “transitional coating and film” means a coatingor film that aids in creating a gradual change in properties orcompatibility between two coatings or films, or a coating and a film.For example, although not limiting herein, a transitional coating canaid in creating a gradual change in hardness between a relatively hardcoating and a relatively soft coating. Non-limiting examples oftransitional coatings include radiation-cured, acrylate-based thin filmsas described in U.S. Pat. No. 7,452,611 B2, which are herebyspecifically incorporated by reference herein.

As used herein, the term “abrasion-resistant coating and film” refers toa protective polymeric material that demonstrates a resistance toabrasion that is greater than a standard reference material, e.g., apolymer made of CR-39® monomer available from PPG Industries, Inc., astested in a method comparable to ASTM F-735 Standard Test Method forAbrasion Resistance of Transparent Plastics and Coatings Using theOscillating Sand Method. Non-limiting examples of abrasion-resistantcoatings can include, but are not limited to, abrasion-resistantcoatings comprising organosilanes, organosiloxanes, abrasion-resistantcoatings based on inorganic materials such as silica, titania and/orzirconia, organic abrasion-resistant coatings of the type that areultraviolet light curable, oxygen barrier-coatings, UV-shieldingcoatings, and combinations thereof. Non-limiting examples of commercialhard coating products include CRYSTALCOAT® and HI-GARD® coatings,available from SDC Coatings, Inc. and PPG Industries, Inc.,respectively.

The abrasion-resistant coating or film (often referred to as a hardcoat) can, with some aspects, be selected from art-recognized hard coatmaterials, such as organosilane abrasion-resistant coatings.Organosilane abrasion-resistant coatings, often referred to as hardcoats or silicone-based hard coatings, are well known in the art, andare commercially available from various manufacturers, such as SDCCoatings, Inc. and PPG Industries, Inc. Reference is made to U.S. Pat.No. 4,756,973 at column 5, lines 1-45; and to U.S. Pat. No. 5,462,806 atcolumn 1, lines 58 through column 2, line 8, and column 3, line 52through column 5, line 50, which disclosures describe organosilane hardcoatings and which disclosures are incorporated herein by reference.Reference is also made to U.S. Pat. Nos. 4,731,264, 5,134,191,5,231,156, and International Patent Publication No. WO 94/20581 fordisclosures of organosilane hard coatings, which disclosures are alsoincorporated herein by reference. The hard coat layer can be applied byart-recognized coating methods such as, but not limited to, rollcoating, spray coating, curtain coating, and spin coating.

Non-limiting examples of suitable antireflective coatings and filmsinclude a monolayer, multilayer or film of metal oxides, metalfluorides, or other such materials, which can be deposited onto thearticles disclosed herein (or onto films that are applied to thearticles), for example, through vacuum deposition, sputtering, etc.Non-limiting examples of suitable conventional photochromic coatings andfilms include, but are not limited to, coatings and films comprisingconventional photochromic materials.

Although the present invention has been described with reference tospecific details of certain embodiments thereof, it is not intended thatsuch details should be regarded as limitations upon the scope of theinvention except insofar as they are included in the accompanyingclaims.

The invention claimed is:
 1. A method for coloring an optical element ina non-uniform linear pattern, the method comprising: (a) preparing atleast one colorant composition comprising at least one photochromicmaterial comprising a photochromic compound selected from the groupconsisting of pyrans, spiropyrans, oxazines, spiroxazines, fulgides,fulgimides, metallic dithizonates, diarylethenes, and mixtures thereof;(b) depositing the colorant composition on at least one surface of theoptical element in a controlled predetermined pattern using an inkjetprinting apparatus so as to provide a linearly gradient color pattern onthe optical element upon exposure of the optical element to actinicradiation, wherein (1) the predetermined pattern is formed by depositionof multiple colorant compositions using an ink jet apparatus comprisedof multiple print heads, and each print head is provided with adifferent colorant composition, or (2) the predetermined pattern isformed by deposition of a single colorant composition deposited in oneor more successive layers using an ink jet apparatus comprising a singleprint head; and (c) drying the colorant composition on the surface ofthe optical element.
 2. The method of claim 1, wherein the opticalelement comprises a substrate having a uniform tinted color prior todeposition of the colorant composition.
 3. The method of claim 1,wherein the colorant composition further comprises at least onepolymeric component.
 4. The method of claim 1, wherein the inkjetapparatus is comprised of multiple print heads, where each print head isprovided with (i) a different colorant composition, and (ii) optionally,a composition free of photochromic material, and wherein eachcomposition is deposited on the surface of the optical element in apredetermined pattern so as to provide a linearly gradient color patternwhich varies in hue and/or color density from one area of the opticalelement to another area of the optical element upon exposure of theoptical element to actinic radiation.
 5. The method of claim 1, whereinthe inkjet apparatus is comprised of multiple print heads, where eachprint head is provided with a different colorant composition, andwherein each composition is deposited on the surface of the opticalelement in a predetermined pattern so as to provide a linearly gradientcolor pattern which varies in hue from one area of the optical elementto another area of the optical element upon exposure of the opticalelement to actinic radiation.
 6. The method of claim 1, wherein thecolorant composition is heated within the inkjet apparatus prior todepositing the colorant composition onto at least one surface of theoptical element.
 7. The method of claim 1, wherein the optical elementis selected from the group consisting of lenses, windows, displayelements, goggles, visors, face shields, automotive transparencies,aerospace transparencies, and wearable displays.
 8. The method of claim7, wherein the optical element is an ophthalmic lens.
 9. The method ofclaim 7, wherein the optical element is a lens, and the linearlygradient color pattern varies in hue and/or color density from thebottom of the lens to the top of the lens upon exposure of the lens toactinic radiation.
 10. The method of claim 9, wherein, upon exposure ofthe lens to actinic radiation, the gradient color pattern has a higherpercent light transmittance at the bottom of the lens than at the top ofthe lens.
 11. The method of claim 1, wherein the colorant compositioncomprises a curable composition comprising at least one photochromic dyeand at least one polymeric component.
 12. The method of claim 1, furthercomprising leveling the colorant composition during the depositing step(b) or immediately thereafter, but prior to the drying step (c).
 13. Themethod of claim 12, wherein the leveling comprises vibrating the opticalelement.
 14. The method of claim 13, wherein the leveling comprisesvibrating the optical element linearly.
 15. The method of claim 14,wherein the leveling comprises vibrating the optical element linearlyalong one axis.
 16. The method of claim 14, wherein the levelingcomprises vibrating the optical element linearly along two axes.
 17. Themethod of claim 14, wherein the leveling comprises vibrating the opticalelement linearly in one plane.
 18. The method of claim 1, wherein theinkjet printing apparatus is a piezo-electric inkjet printing apparatus.19. The method of claim 1, wherein the inkjet printing apparatus is athermal inkjet printing apparatus.